Some ideas for kids' Halloween costumes.
Cut paper plates to appropriate size for box.
Creating Rosie's window and siding.
The box should be dry now. Paint it the main color of the train that you're making.
Start to shape the body of the character. The details shown here are made from white paper bags fastened with hot glue. You can just paint them on also.
Paint another paper bag black for the coal.
Lesson learned: Never go trick-or-treating in the cold rain.